pygmt.grdcut

pygmt.grdcut(grid, **kwargs)[source]

Extract subregion from a grid.

Produce a new outgrid file which is a subregion of grid. The subregion is specified with region; the specified range must not exceed the range of grid (but see extend). If in doubt, run pygmt.grdinfo to check range. Alternatively, define the subregion indirectly via a range check on the node values or via distances from a given point. Finally, you can give projection for oblique projections to determine the corresponding rectangular region that will give a grid that fully covers the oblique domain.

Full option list at https://docs.generic-mapping-tools.org/6.5/grdcut.html

Aliases:

  • G = outgrid

  • J = projection

  • N = extend

  • R = region

  • S = circ_subregion

  • V = verbose

  • Z = z_subregion

  • f = coltypes

Parameters:

  • grid (str or xarray.DataArray) –

    Name of the input grid file or the grid loaded as a xarray.DataArray object.

    For reading a specific grid file format or applying basic data operations, see https://docs.generic-mapping-tools.org/6.5/gmt.html#grd-inout-full for the available modifiers.

  • outgrid – Name of the output netCDF grid file. If not specified, will return an xarray.DataArray object. For writing a specific grid file format or applying basic data operations to the output grid, see https://docs.generic-mapping-tools.org/6.5/gmt.html#grd-inout-full for the available modifiers.

  • projection (str) – projcode[projparams/]width|scale. Select map projection.

  • region (str or list) – xmin/xmax/ymin/ymax[+r][+uunit]. Specify the region of interest.

  • extend (bool or float) – Allow grid to be extended if new region exceeds existing boundaries. Give a value to initialize nodes outside current region.

  • circ_subregion (str) – lon/lat/radius[unit][+n]. Specify an origin (lon and lat) and radius; append a distance unit and we determine the corresponding rectangular region so that all grid nodes on or inside the circle are contained in the subset. If +n is appended we set all nodes outside the circle to NaN.

  • z_subregion (str) – [min/max][+n|N|r]. Determine a new rectangular region so that all nodes outside this region are also outside the given z-range [-inf/+inf]. To indicate no limit on min or max only, specify a hyphen (-). Normally, any NaNs encountered are simply skipped and not considered in the range-decision. Append +n to consider a NaN to be outside the given z-range. This means the new subset will be NaN-free. Alternatively, append +r to consider NaNs to be within the data range. In this case we stop shrinking the boundaries once a NaN is found [Default simply skips NaNs when making the range decision]. Finally, if your core subset grid is surrounded by rows and/or columns that are all NaNs, append +N to strip off such columns before (optionally) considering the range of the core subset for further reduction of the area.

  • verbose (bool or str) –

    Select verbosity level [Default is w], which modulates the messages written to stderr. Choose among 7 levels of verbosity:

    • q - Quiet, not even fatal error messages are produced

    • e - Error messages only

    • w - Warnings [Default]

    • t - Timings (report runtimes for time-intensive algorithms)

    • i - Informational messages (same as verbose=True)

    • c - Compatibility warnings

    • d - Debugging messages

  • coltypes (str) – [i|o]colinfo. Specify data types of input and/or output columns (time or geographical data). Full documentation is at https://docs.generic-mapping-tools.org/6.5/gmt.html#f-full.

Return type:

DataArray | None

Returns:

ret – Return type depends on whether the outgrid parameter is set:

  • xarray.DataArray if outgrid is not set

  • None if outgrid is set (grid output will be stored in the file set by outgrid)

Example

>>> import pygmt
>>> # Load a grid of @earth_relief_30m data, with a longitude range of
>>> # 10° E to 30° E, and a latitude range of 15° N to 25° N
>>> grid = pygmt.datasets.load_earth_relief(
...     resolution="30m", region=[10, 30, 15, 25]
... )
>>> # Create a new grid from an input grid, with a longitude range of
>>> # 12° E to 15° E and a latitude range of 21° N to 24° N
>>> new_grid = pygmt.grdcut(grid=grid, region=[12, 15, 21, 24])